Authorship order is of increasing importance for scientific careers and the success of collaborations. This is especially true in biological sciences, where the first author typically makes the greatest contribution and the last has a leadership role. The process of choosing the order needs to foster understanding and accountability, while recognizing each author's contribution. This can be difficult. So how does a group get it right? We have devised a model for finding the best order, avoiding conflict and promoting long-term collaborations. First step: you need to discuss authorship before starting the project, and again while you prepare the manuscript and make revisions.

Using a multi-criterion decision making (MCDM) approach, a group of potential co-authors decides on a set of items — such as figures, tables, text and ideas — that comprise a manuscript. They score each person's contribution to each item as a percentage. Types of contribution vary across publications, but a group of co-authors is well placed to make judgements. As they may not always agree exactly, a range can be assigned that they can 'agree to disagree' on.

The group should then assess the relative importance of each item and put them in categories, in order of importance to the manuscript. For example, category A (the most important) might constitute a 15% weighting, category B 10% and category C 5%. This way, each item is given a weighting that represents its importance to the whole work. Finally, each author's relative contribution to each item is calculated.

It's important to work out authors' contributions to each item first, as this is likely to be simpler than assessing categories and weighting. A culture of understanding and agreement about the relative importance of different activities will help the process to run smoothly. In our system, co-authors are encouraged to appreciate different perspectives and negotiate on criteria. This process should enhance scientific best practice and increase researcher accountability.

The MCDM approach enables a rational, project-specific account of all factors that led to the publication. It's of particular use for multidisciplinary work and for teams with different experiences and at different stages of their careers. Focusing on items one at a time helps to resolve potential conflict, encourages authors to value other perspectives and helps to clarify any ambiguity over contributions.